let a = "10";
let b: 12;

let c: 0 | 1 | 2;
c = 0;
c = 1;
c = 2;

let d;
d = 0;
d = "hello";

let e: unknown;
e = 98;
e = true;
e = "99";
 e = d;
 d = e;

let f: string;
f = "20";
if (typeof f === "string") {
  f = d;
  console.log("走进来");
}
f = <string>d;
f = d as string;

function fn1():void {
    console.log("新")
}
fn1();
function fn2():never {
    throw new Error("我是error")
}
fn2()

export {};